Multi-layer films comprising propylene-based polymers

Abstract

This disclosure relates to multi-layer films having improved peel strength properties and comprising a core layer and a first tie layer made from at least 5 wt % of a grafted propylene-based polymer. Optionally, the multi-layer film may have one or more skin layers, and/or a second tie layer.

1. A multi-layer film, comprising:
 a. a core layer; and 
 b. a first tie layer comprising at least 10 wt % grafted propylene-based polymer, based upon the weight of the first tie layer, the grafted propylene-based polymer comprising a propylene-based polymer backbone having from about 5 to about 24 wt % ethylene, and a grafting monomer, the grafted propylene-based polymer having a DSC melting temperature of 120° C. or less and a heat of fusion of 75 J/g or less. 
 
     
     
       2. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has isotactic propylene crystallinity. 
     
     
       3. The multi-layer film of  claim 1 , wherein the multi-layer film further comprises a first skin layer, the first tie layer being intermediate the core layer and the first skin layer. 
     
     
       4. The multi-layer film of  claim 3 , wherein the first skin layer is a barrier layer. 
     
     
       5. The multi-layer film of  claim 4 , wherein the barrier layer comprises at least one moisture barrier additive or gas barrier additive. 
     
     
       6. The multi-layer film of  claim 3 , wherein the first skin layer comprises at least one polar polymer. 
     
     
       7. The multi-layer film of  claim 1 , wherein the grafting monomer is selected from the group consisting of maleic anhydride, methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate and combinations thereof. 
     
     
       8. The multi-layer film of  claim 1 , wherein the first tie layer comprises at least 20 wt % of the grafted propylene-based polymer. 
     
     
       9. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a DSC melting temperature less than 105° C. 
     
     
       10. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a DSC melting temperature of less than 90° C. 
     
     
       11. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a DSC melting temperature of less than 75° C. 
     
     
       12. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer comprises from about 5 to about 16 wt % ethylene. 
     
     
       13. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer comprises from about 8 to about 15 wt % ethylene. 
     
     
       14. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a melt flow rate of 25 g/10 min (at 190° C., 1.2 kg) or less. 
     
     
       15. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a melt flow rate equal to or greater than 0.2 g/10 min (at 190° C., 1.2 kg). 
     
     
       16. The multi-layer film of  claim 1 , wherein the first tie layer further comprises one or more other C 2 -C 8  copolymers or terpolymers. 
     
     
       17. The multi-layer film of  claim 1 , wherein the film is biaxially oriented. 
     
     
       18. The multi-layer film of  claim 1 , wherein the film is un-oriented. 
     
     
       19. The multi-layer film of  claim 1 , wherein the film is uniaxially oriented. 
     
     
       20. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a triad tacticity index of at least 75%. 
     
     
       21. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a Mooney viscosity ML (1+4)@125° C. of less than 100. 
     
     
       22. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a % crystallinity of from about 0.5 to about 40. 
     
     
       23. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a crystallization temperature (Tc) measured with differential scanning calorimetry (DSC) of about 160° C. or less. 
     
     
       24. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a density of about 0.85 to about 0.92 g/cm 3 . 
     
     
       25. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a molecular weight distribution of from about 1.5 to about 40.0. 
     
     
       26. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a weight average molecular weight (Mw) of about 5,000,000 or less, a number average molecular weight (Mn) of about 3,000,000 or less, a z-average molecular weight (Mz) of about 10,000,000 or less, and a g′ index of about 0.95 or greater. 
     
     
       27. The multi-layer film of  claim 1 , wherein the propylene-based polymer backbone monomers are polymerized in the presence of a metallocene catalyst system. 
     
     
       28. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer comprises propylene, ethylene, and optionally a non-conjugated diene, with propylene being the majority component. 
     
     
       29. The multi-layer film of  claim 28 , wherein the grafted propylene-based polymer comprises propylene, ethylene, and optionally 5 -ethylidene-2-norbornene (ENB), with propylene being the majority component. 
     
     
       30. The multi-layer film of  claim 1 , wherein the grafted propylene-based polymer has a melt flow rate of about 1.0 to about 15.0 g/10 min (230° C., 2.16 kg). 
     
     
       31. The multi-layer film of  claim 1 , wherein the first tie layer further comprises an ethylene alpha-olefin copolymer in an amount of about 1-95 wt %, based upon the weight of the first tie layer. 
     
     
       32. The multi-layer film of  claim 1 , wherein the first tie layer further comprises one or more other polypropylene homopolymers or random copolymers. 
     
     
       33. The multi-layer film of  claim 1 , wherein the core layer comprises at least one polymer selected from the group consisting of propylene polymers, ethylene polymers, isotactic polypropylene, ethylene-propylene copolymers and combinations thereof. 
     
     
       34. The multi-layer film of  claim 1 , wherein the core layer further comprises at least one additive selected from the group consisting of opacifying agents, void-initiating particles, hydrocarbon resins, fillers, anti-static agents, and combinations thereof. 
     
     
       35. The multi-layer film of  claim 3 , wherein at least one of the core layer, first tie layer and/or first skin layer further comprises at least one additive selected from the group consisting of opacifying agents, cavitating agents, nucleating agents, clarifying agents, fillers, anti-blocks, anti-static agents, coefficient of friction (COF) modifiers, processing aids, colorants, and combinations thereof. 
     
     
       36. The multi-layer film of  claim 3 , wherein at least a portion of at least one of the outer surfaces of the film is metallized. 
     
     
       37. The multi-layer film of  claim 3 , wherein at least a portion of at least one of the outer surfaces of the film is surface-treated. 
     
     
       38. The multi-layer film of  claim 37 , wherein the surface treatment is selected from the group consisting of corona discharge, flame, plasma, chemical treatment, treatment by means of a polarized flame, and combinations thereof. 
     
     
       39. The multi-layer film of  claim 3 , wherein at least a portion of at least one of the outer surfaces of the film is contacted with one or more coatings. 
     
     
       40. The multi-layer film of  claim 39 , wherein the one or more coatings is selected from the group consisting of acrylic polymers, such as ethylene acrylic acid (EAA), ethylene methyl acrylate copolymers (EMA), polyvinylidene chloride (PVdC), poly(vinyl)alcohol (PVOH), EVOH, Polyamide (PA), Polyethylene terephtalate (PET), and combinations thereof. 
     
     
       41. The multi-layer film of  claim 39 , wherein the coatings are applied by a method selected from the group consisting of an emulsion coating technique, by co-extrusion, lamination, and combinations thereof. 
     
     
       42. A method of improving the peel resistance of a multi-layer film by forming a film comprising: a core layer and a first tie layer comprising at least 10 wt % grafted propylene-based polymer, based upon the weight of the first tie layer, the grafted propylene-based polymer comprising a propylene-based polymer backbone having from about 5 to about 24 wt % ethylene, and a grafting monomer, the grafted propylene-based polymer having a DSC melting temperature of 120° C. or less and a heat of fusion of 75 J/g or less. 
     
     
       43. A multi-layer film comprising:
 a. a core layer; 
 b. a first tie layer comprising at least 10 wt % grafted propylene-based polymer, based upon the weight of the layer, the grafted propylene-based polymer comprising a propylene-based polymer backbone having from about 3 to about 24 wt % ethylene and/or a C 4 -C 20  olefin, and a grafting monomer, the grafted propylene-based polymer having a DSC melting temperature of 120° C. or less and a heat of fusion of 75 J/g or less; 
 c. a first skin layer, wherein the first tie layer is located intermediate the core layer and the first skin layer; and 
 d. a second skin layer located on the opposite side of the core layer from the first tie layer. 
 
     
     
       44. A multi-layer film comprising;
 a. a core layer; 
 b. a first tie layer comprising at least 10 wt % grafted propylene-based polymer based upon the weight of the layer, the grafted propylene-based polymer comprising a propylene-based polymer backbone having from about 5 to about 24 wt % ethylene, and a grafting monomer, the grafted propylene-based polymer having a DSC melting temperature of 120° C. or less and a heat of fusion of 75 J/g or less; 
 c. a first skin layer, wherein the first tie layer is located intermediate of the core layer and the first skin layer; 
 d. a second tie layer located on a side of the core layer opposite from the first tie layer; and 
 e. a second skin layer, wherein the second tie layer is located intermediate the core layer and the second skin layer. 
 
     
     
       45. The multi-layer film of  claim 44 , wherein the first tie layer and the second tie layer are made from and/or comprise the same material. 
     
     
       46. The multi-layer film of  claim 44 , wherein the first tie layer and the second tie layer are made from and/or comprise one or more different materials. 
     
     
       47. A process comprising forming a multi-layer film comprising: a core layer and a first tie layer, the first tie layer comprising at least 10 wt % grafted propylene-based polymer, based upon the weight of the layer, the grafted propylene-based polymer comprising a propylene-based polymer backbone having from about 5 to about 24 wt % ethylene, and a grafting monomer, the grafted propylene-based polymer having a DSC melting temperature of 120° C. or less and a heat of fusion of 75 J/g or less. 
     
     
       48. The multi-layer film of  claim 1 , wherein the first tie layer further comprises a propylene polymer in an amount of about 5-90 wt %, based upon the weight of the first tie layer.